 GeeksforGeeks App
Open App Browser
Continue

# Python | Find maximum length sub-list in a nested list

Given a list of lists, write a Python program to find the list with maximum length. The output should be in the form (list, list_length)

Examples:

```Input : [['A'], ['A', 'B'], ['A', 'B', 'C']]
Output : (['A', 'B', 'C'], 3)

Input : [[1, 2, 3, 9, 4], , [3, 8], ]
Output : ([1, 2, 3, 9, 4], 5)```

Let’s discuss different approaches to solve this problem.

Approach #1 : Using for loop (Naive) This is a brute force method in which we iterate through each list item(list) and find the list with maximum length. Similarly, we use the for loop to find length of each list and output the maximum length.

## Python3

 `# Python3 program to Find maximum``# length list in a nested list` `def` `FindMaxLength(lst):``    ``maxList ``=` `max``((x) ``for` `x ``in` `lst)``    ``maxLength ``=` `max``(``len``(x) ``for` `x ``in` `lst )` `    ``return` `maxList, maxLength``    ` `# Driver Code``lst ``=` `[[``'A'``], [``'A'``, ``'B'``], [``'A'``, ``'B'``, ``'C'``]]``print``(FindMaxLength(lst))`

Output:

`(['A', 'B', 'C'], 3)`

Time Complexity: O(N)
Auxiliary Space: O(1)

Approach #2: Using map In this method we use Python map function to iterate over the inner lists to create a list of lengths, then get the maximum with max function.

## Python3

 `# Python3 program to Find maximum``# length list in a nested list` `def` `FindMaxLength(lst):``    ``maxList ``=` `max``(lst, key ``=` `len``)``    ``maxLength ``=` `max``(``map``(``len``, lst))``    ` `    ``return` `maxList, maxLength` `# Driver Code``lst ``=` `[[``'A'``], [``'A'``, ``'B'``], [``'A'``, ``'B'``, ``'C'``], ]``print``(FindMaxLength(lst))`

Output:

`(['A', 'B', 'C'], 3)`

Time Complexity: O(N)
Auxiliary Space: O(N)

Approach #3: Using lambda operator One more method in Python to find the longest length list is the lambda operator. It is used for creating small, one-time and anonymous function objects in Python. Here we pass a variable i as argument in the len(i) expression and find the maximum length.

## Python3

 `# Python3 program to Find maximum``# length list in a nested list` `def` `FindMaxLength(lst):``    ``maxList ``=` `max``(lst, key ``=` `lambda` `i: ``len``(i))``    ``maxLength ``=` `len``(maxList)``    ` `    ``return` `maxList, maxLength``# Driver Code``lst ``=` `[[``'A'``], [``'A'``, ``'B'``], [``'A'``, ``'B'``, ``'C'``]]``print``(FindMaxLength(lst))`

Output:

`(['A', 'B', 'C'], 3)`

Time Complexity: O(N)
Auxiliary Space: O(1)

Approach 4: use list comprehension

This approach uses the built-in len function and list comprehension to find the maximum length list. The max function takes an argument key which specifies a function to determine the maximum value. In this case, we use len as the key function to find the list with the maximum length.

## Python3

 `def` `FindMaxLength(lst):``    ``maxList ``=` `max``(lst, key``=``len``)``    ``maxLength ``=` `len``(maxList)``    ` `    ``return` `maxList, maxLength` `# Driver Code``lst ``=` `[[``'A'``], [``'A'``, ``'B'``], [``'A'``, ``'B'``, ``'C'``]]``print``(FindMaxLength(lst))`

Output

`(['A', 'B', 'C'], 3)`

Time complexity: O(n) because it iterates through each list only once to find the maximum length.
Auxiliary space: O(1) because it does not create any additional data structures.

My Personal Notes arrow_drop_up